Added hover_pressed style to CheckBox and CheckButton

[Piet-G]

Added hover_pressed style to CheckBox and CheckButton.
If no style is defined for this styleit will default to the pressed style.

This fixes #19429

[akien-mga]

Thanks!

[akien-mga]

This added two warnings (GCC 5):

scene/gui/link_button.cpp: In member function 'void LinkButton::_notification(int)':
scene/gui/link_button.cpp:71:11: warning: enumeration value 'DRAW_HOVER_PRESSED' not handled in switch [-Wswitch]
    switch (get_draw_mode()) {
           ^
scene/gui/texture_button.cpp: In member function 'void TextureButton::_notification(int)':
scene/gui/texture_button.cpp:125:11: warning: enumeration value 'DRAW_HOVER_PRESSED' not handled in switch [-Wswitch]
    switch (draw_mode) {
           ^

[Piet-G]

Is that a problem? Since those buttons don't really have to deal with the HOVER_PRESSED mode.

[akien-mga]

It's not a problem per se, but the aim of this warning is to make sure we don't forget to handle enum values in switches where it would actually be relevant. If it isn't for those two, a case DRAW_HOVER_PRESSED: break; // Not relevant here makes it clear for all code readers (and silences the warning). See #22447.

[akien-mga]

I can fix it myself as I'm working on warnings right now, I just wanted to check if it was an omission or indeed not relevant for those two nodes.

[Piet-G]

Yeah it is only relevant for buttons where being pressed does not imply hovering.